In various fields such as seawater desalination and ultrapure water production for semiconductor manufacturing and further general-purpose brackish water desalination, organic matter separation, and wastewater recycle, various fluid separation devices using separation membranes are used to obtain permeate that has passed through the membrane or condensate as a valuable product. Such a fluid separation device generally comprises a fluid separation element using a separation membrane and a pressure vessel into which the fluid separation element is loaded.
Examples of such a fluid separation element using a separation membrane include a fluid separation element using a hollow fiber membrane, a plate frame-type fluid separation element and a spiral-type fluid separation element using a flat sheet membrane.
A spiral-type fluid separation element has a structure in which a separation membrane, a permeate channel material, and a feed liquid channel material are spirally wound around a water collection tube. An example of a fluid separation element having such a structure is shown in FIG. 1.
The fluid separation element shown in FIG. 1 uses an envelope-shaped membrane comprising a first separation membrane 13 and a second separation membrane 14. The envelope-shaped membrane is formed by bonding two membranes together at three sides or by folding a membrane in two. A permeate channel material 15 is inserted into the envelope-shaped membrane. The envelope-shaped membrane having the permeate channel material 15 therein and a feed water channel material 16 form one unit. A membrane winding 1 is formed by spirally winding the unit around a water collection tube 11 or by layering the two or more units and spirally winding the layered units around the water collection tube 11. The envelope-shaped membrane opens on the water collection tube 11 side. Two anti-telescoping devices 2 are attached to both longitudinal ends of the membrane winding 1.
Feed water 12 flows from one of the ends of the fluid separation element into the membrane winding 1 through the upstream-side anti-telescoping device 2u. The feed water 12 is separated into permeate 18 that has passed through the first separation membrane 13 and the second separation membrane 14 and condensate 17 that has not passed through the first separation membrane 13 and the second separation membrane 14. The permeate 18 having passed through the separation membranes 13 and 14 flows through the permeate channel material 15, and is collected by the water collection tube 11 and discharged from the fluid separation element. On the other hand, the feed water 12 not having passed through the separation membranes 13 and 14 passes through the downstream-side anti-telescoping device 2d, and is discharged through the other end of the fluid separation element as the condensate 17.
The outer circumferential surface of the membrane winding 1 of the spiral-type fluid separation element is generally twisted and hardened into a shell by a fiber reinforced plastic (FRP) composed of glass fiber and epoxy resin.
A sealing member called “brine seal” is attached to the outer circumferential surface of the upstream-side anti-telescoping device 2u attached to the fluid separation element. When feed water is allowed to flow into the fluid separation element housed in the pressure vessel, the brine seal prevents the feed water from flowing into the gap between the FRP shell provided outside the fluid separation element and the pressure vessel, that is, prevents the short-pass of the feed water.
In order to attach an annular brine seal, a groove is provided in the outer circumferential surface of the anti-telescoping device. The brine seal is attached by fitting it into the groove (see, for example, JP-A-2005-111473 or JP-A-2006-212514).
The cross-sectional shape of the brine seal fitted into the groove provided in the outer circumferential surface of the anti-telescoping device is not particularly limited, and therefore the brine seal may be, for example, an O-ring or an X-ring, but a U-seal having a U-shaped cross section is often used from the viewpoint of loading the fluid separation element into the pressure vessel. In order to obtain an optimum sealing effect, the U-seal needs to be fitted into the groove so that the upper portion of the U-shape faces the upstream side (feed water inlet side). However, there is a case where the U-seal made of an elastic resin is twisted when fitted into the groove. If the U-seal fitted into the groove of the anti-telescoping device remains twisted, a desired sealing effect cannot be obtained when the fluid separation element is charged into the pressure vessel. For this reason, the twisted U-seal needs to be once removed from the groove to fit the U-seal into the groove again. At this time, the U-seal needs to be removed from the groove without damage to the brine seal and the anti-telescoping device.
Meanwhile, JP-A-2005-111473 proposes that one of the side walls of a brine seal fitting groove is made lower than the other side wall or is partially cut out, but this proposal is not intended to remove a brine seal from the groove. However, also in this case, a tool having a sharp tip needs to be inserted into the groove to remove a sealing material. When a pointed tool is inserted between an anti-telescoping device and a sealing material, both the anti-telescoping device and the sealing material are likely to be damaged. On the other hand, when a sealing material is removed by pressing a tool against a sealing functional part of the sealing material and pulling up the sealing material, the sealing functional part is likely to be damaged.